Various glycosidases are known as an enzyme which is widely distributed in animal cells, microorganisms, viruses, etc. In mammalian animals, it has been considered that glycosidases control a great variety of physiological mechanisms, including canceration of normal cells, metastasis of cancer cells, viral or bacterial infection, immunological functions, fertilization of an ovum, and others in which glycoproteins and glycolipid-glycosyl chains participate through the carbohydrate metabolism. Moreover, certain glycosidases participate in the digestive mechanism of food through the degradation of polysaccharides such as starch, sucrose, and oligosaccharides etc. Furthermore, it has been found that a substance inhibitory to a glycosidase which can liberate the glycosyl chains as combined in a cell membrane is possible to have an immunomodulating action and an action which controls the metastasis of cancer cells, as well as an action which controls infection of an AIDS virus or an influenza virus. Moreover, substances inhibitory to a glycosidase having catabolism which participates in the digestive mechanism of food are found to be important, since they are useful as an antidiabetic agent or an antiobestic agent.
Thus, in view that a glycosidase is an enzyme which is important in the living body, it is also important to study physiological properties of a glycosidase. In the study of the properties of a glycosidase, use can be made of such a substance having an action which inhibits the enzymatic activity of a glycosidase. Moreover, it can be expected that certain glycosidase-inhibitory substances can be utilized as an inhibitor to the metastasis of cancer cells. Therefore, it has been keenly demanded to provide such a novel compound which is of low toxicity, which is water-soluble and which has a potent glycosidase-inhibitory activity.
It is an object of this invention to provide a novel siastatin B derivative which exhibits a potent activity inhibitory to a glycosidase. Moreover, it is another object of this invention to provide processes for producing such a new siastatin B derivative.
It are still another objects to provide a pharmaceutical composition comprising as an active ingredient said siastatin B derivative having the glycosidase-inhibitory activity, and also to provide a glycosidase inhibitor consisting of said siastatin B derivative.